That depends on what you are trying to achieve, the best basic practice for two players is the Boast and Drive,
Player A at the front plays straight drives (down the wall within two boards of the wall) Player B at the back plays a boast from each back corner (aiming to get the front side wall nick off the boast).
Both players must return to the T after each shot.
Try putting something in the middle of the court that each player has to touch between their shot.
(we used to use an old fire extinguisher because you could hear when a player failed to touch it! No ting!)
Change over after about 4 mins.
The above practice trains for fitness, racket technique (preparation) and ball placement.
Once you have mastered the basic Boast / Drive practice you can change it so that Player A (at the front) can play either straight or cross court drives. (starting to get harder!)